> Thank you for the tip of not starting the topics with a slash (/), but all things being equal,
> it would not be the cause of message ingestion rate dropping as the number of
> consumers grows, would it?
Right, but it was just an optimization remark :)
> This does sound like the topic to subscription matching bottleneck, doesn't it?
Yes, but it looks to me more a bottleneck at Mosquitto side instead of client one.